Favreau directed the first two films in the superhero saga and reprises his cameo role as Tony Stark's bodyguard Happy Hogan in the hugely successful current third film in the series. He will take the lead role in Chef, which centres on a sacked restaurant worker who starts up a food truck to reclaim his artistic promise and simultaneously finds himself reclaiming his estranged family.

The film, which begins shooting next month in LA, also stars Sofia Vergara, John Leguizamo and Bobby Cannavale. It is not yet known which role Downey Jr will play.

Favreau made his name in front of the cameras on the Doug Liman indie comedy drama Swingers, which he also wrote, in 1996, and has oscillated between directing and acting ever since. Despite the low-key nature of Chef, he maintains an interest in blockbuster film-making: future projects include the Disney film Magic Kingdom, about a family which travels to Disneyland and sees its famous inhabitants come to life.

He's best known for a couple of cult TV shows and the odd, welcome film cameo. Yet Jeffrey Tambor's acting workshop is the hottest ticket at the South by Southwest festival in Austin, Texas. He talks about his mission to instil confidence